The present invention relates to an apparatus for generating a base station clock; and more particularly, to an apparatus for controlling a global positioning system (GPS) reference signal to be provided to a base station modem to thereby expand a coverage area of the base station.
In general, a base station modem is operated based on a reference signal /pp2s (pulse per 2 seconds) and a system clock (19.6608 MHz) provided thereto from a global positioning system (GPS). In this case, a terminal transmits signals in synchronism with a Sync channel provided from the base station.
However, the signal provided from the terminal in the base station modem is delayed than time of the GPS reference signal/pp2s, and the base station modem can demodulate (call) signals with less delay than about 512PN chip (416.67 xcexcsec), wherein 416.67 xcexcsec will come to about 60 km in length.
In short, if signals transmitted from a terminal are received by the base station, the terminal being positioned at a distance more than about 60 km from the base station, the base station modem fails to demodulate the received signals to fail calling. In addition, a limited call coverage allows calling in a location at which the base station cannot be installed to be failed.
It is, therefore, a primary object of the present invention to provide an apparatus, which is capable of delaying a GPS reference signal to be forwarded to a base station modem for a certain time period and transmitting a delayed signal to the modem, to thereby establish calling between the base station and a terminal located at a certain distance from the base station.
In accordance with a preferred embodiment of the present invention, there is provided an apparatus for generating a clock signal used to expand a coverage area of a base station, which comprises: a clock reception means for generating a system clock and a pp2s (pulse per 2 seconds) signal based on a reference time provided from a global positioning system (GPS); a clock distribution means for distributing the system clock received from the clock reception means; a clock generation means for generating clock signals as base station synchronous signals to expand the coverage area by receiving the pp2s signal from the clock reception means; a multiplicity of base station modems for modulating/demodulating data in synchronism with the clock signal transmitted from the clock generation means; a control signal generation means for generating control signals; and a control means for allowing the data to be transmitted to a selected base station modem among the base station modems in response to a corresponding control signal from the control signal generation means.